The work proposed is a genetic study of mutants affecting development in the cellular slime mold, Polysphondylium pallidum. The mutants are generated by nitrosoquanidine mutagenesis and characterized by deficiencies in the set of polypeptides which show changes in label incorporation during normal development. Crosses are to be made using the macrocyst sexual system, and complementation studies will be performed via a parasexual system. Particular experiments are: 1) To describe by two-dimensional electrophoresis labeling changes in a subset of about 12 developmental mutants already known to have deficiencies in labeling. 2) To count the number of loci represented in these mutants by a matrix of complementation crosses. 3) To map the different loci by means of macrocyst crosses. Of particular interest will be the identification of distinct, linked loci affecting a single phase of development. 4) The above genetic experiments depend on a two mating type system. A homozygous sexual system, in which each mutation can be examined against the same genetic background, will be sought as well.